1. Field of the Invention
The present invention relates to a hydraulic control apparatus of an automatic transmission mounted in a vehicle or the like, and particularly, relates to a hydraulic control apparatus of an automatic transmission with which oil passages for discharging an oil pressure from a hydraulic servo of a frictional engagement element are made switchable.
2. Description of the Related Art
In general, with a multi-stage automatic transmission mounted in a vehicle or the like, each speed stage is formed by controlling a rotation condition of each rotational element of a speed change gear mechanism using an engagement condition of a plurality of frictional engagement elements, and the engagement condition of the plurality of frictional engagement elements is controlled by an engagement pressure being electrically adjusted using a solenoid valve and supplied to a hydraulic servo of each frictional engagement element.
Meanwhile, with an automatic transmission disclosed in JP-A-2006-112503, as shown in FIGS. 3 and 4 of the same document, a pressure output from a manual valve (4100) is supplied to a hydraulic servo of a B2 brake, at a reverse range formation time (R), via an R range pressure oil passage (4104), a B2 control valve (4600), and a B2 oil passage (3622), whereby the B2 brake is engaged. Then, when the manual valve (4100) switches from an R range to an N range or a D range, the oil pressure of the hydraulic servo of the B2 brake is swiftly discharged from a drain port (EX) of the manual valve (4100) via the B2 oil passage 3622, B2 control valve (4600), and R range pressure oil passage (4104), in the order opposite to that at a supply time.